1. Field of the Invention
This invention relates to devices for casting cementitious building blocks and more particularly to a combination die and pallet assembly upon which mortarless interlocking cementitious blocks are cast with a plurality of male projections.
2. Description of the Prior Art
Due to the shortage of skilled craftsmen and high labor costs, the search for and development of practical and easy to use mortarless interlocking cementitious blocks has intensified in recent years. One such block, which is beginning to receive general acceptance in the market place, is fully disclosed in U.S. patent application Ser. No. 799,725, filed on May 23, 1977 by the same inventor. Briefly, that mortarless interlocking cementitious block is formed with the conventional rectangular configuration having a pair of vertical passages formed therethrough, and is provided with a plurality of frustro-conical recesses in one of the horizontal surfaces, and complimental frustro-conical male projections on the opposite surface. The recesses and projections are disposed in identical predetermined arrays, and are the block interlocking elements which allows the blocks to be laid in an accurately level and aligned manner by relatively unskilled laborers.
These particular mortarless interlocking cementitious blocks are cast in special mold box assemblies which are used in conjunction with conventional block making machines, with the mold boxes designed to simultaneously cast a plurality of such blocks for production efficiency purposes. The special mold box assembly includes a special head die which forms the frustro-conical female recesses and the top horizontal surface in which they are formed, a special mold box die which forms the side wall configuration and vertical passages of the block, and a special combination die and pallet which forms the frustro-conical male projections and the bottom horizontal surface from which they project.
After the blocks are cast in the above described mold box assembly, the head die is raised and the combination die-pallet structure is lowered with such lowering causing the blocks to be withdrawn from the bottom of the mold box die, and they remain in position atop the die-pallet for subsequent handling. The subsequent handling includes transporting of the die-pallet structure, with the blocks supported thereon, from the block making machine to a kiln for curing. After curing, the die-pallet structure and blocks are again transported, this time from the kiln to a machine which removes the blocks from the die-pallet structure. From this point, the die-pallet structures are routed through suitable cleaning and lubricating mechanisms and are returned to the block making machine for reuse.
Since the combination die-pallet structure is an integral part of the casting operation with the integrity of the blocks themselves being partially dependent thereon, it is extremely important that they be dimensionally accurate and stable, perfectly flat, and otherwise precision structures. In addition to the required precision and stability, the combination die-pallet structures must be: sufficiently strong to resist damage which can and sometimes does occur during the above described subsequent handling operations, easy to repair in the event of damage, and must resist rust out as a result of long periods of exposure to moisture.
Heretofore, the combination die-pallet structures employed have been sheet metal structures fabricated with an upper and a lower plate which are welded together with reinforcing ribs interposed therebetween. Basic configurations of these laminated honeycombed sheet metal die-pallet structures are fully disclosed in U.S. Pat. Nos. 3,998,423 issued Dec. 21, 1976; 4,078,760 issued Mar. 14, 1978; and 4,093,174 issued June 6, 1978, all to the same inventor. These prior art combination die-pallet structures although serving the purpose have some shortcomings, in that they are relatively expensive to manufacture, are subject to damage such as denting, bending and the like, are somewhat difficult to repair, and are subject to rust out.
Therefore, a need exists for a new and improved combination die-pallet assembly which overcomes some of the problems and shortcomings of the prior art.